As a semiconductor material that can be used in a transistor, an oxide semiconductor has been attracting attention. For example, Patent Document 1 discloses a semiconductor device achieving high field-effect mobility (simply referred to as mobility or μFE in some cases) with a structure where a plurality of oxide semiconductor layers are stacked, and among the plurality of oxide semiconductor layers, an oxide semiconductor layer serving as a channel contains indium and gallium and has a higher indium content than a gallium content.
Non-Patent Document 1 discloses that an oxide semiconductor containing indium, gallium, and zinc has a homologous series represented by In1−xGa1+xO3(ZnO)m (x is a number which satisfies −1≤x≤1, and m is a natural number). Furthermore, Non-Patent Document 1 discloses a solid solution range (solid solution range) of a homologous series. For example, in the solid solution range of the homologous series in the case where m=1, x ranges from −0.33 to 0.08, and in the solid solution range of the homologous series in the case where m=2, x ranges from −0.68 to 0.32.